It would appear that there is no significant difference in capacity and voltage between these two examples. But this really is not the case. The plates designed for the T-105 use the same active material and alloy of the group 27 deep cycle batteries but both the T-105 negative and positive plates are 60% thicker than those found in the deep cycle 27 group sizes. The significance of this is that these 6 Volt batteries should have a longer lifespan than the two deep cycle 27 group sizes, if properly cared for. While the capacities are similar (220 versus 225 Amp Hrs.), battery longevity favors the two 6 Volt batteries. Why? Because a major cause of deep cycle battery failure is the shedding of active material from the battery plates.